The present invention relates generally to medical treatments. More specifically, the present invention relates to the synchronization of various fluids used to treat renal failure, fluid overload, congestive heart failure, drug overdoses, poisonings, immune disorders, sepsis and/or acid balance imbalances.
Due to disease, insult or other causes, a person's renal system can fail. In renal failure of any cause, there are several physiological derangements. The balance of water, minerals and the excretion of daily metabolic load are reduced or no longer possible in renal failure. During renal failure, toxic end products of nitrogen metabolism (e.g., urea, creatinine, uric acid, and others) can accumulate in blood and tissues.
Kidney failure and reduced kidney function have been treated with dialysis. Dialysis removes waste, toxins and excess water from the body that would otherwise have been removed by normal functioning kidneys. Dialysis treatment for replacement of kidney functions is critical to many people because the treatment is life sustaining. One who has failed kidneys could not continue to live without replacing at least the filtration functions of the kidneys.
Hemodialysis (“HD”), hemofiltration, hemodiafiltration and peritoneal dialysis are types of dialysis therapies generally used to treat loss of kidney function. Peritoneal dialysis utilizes a sterile dialysis solution, or “dialysate”, which is infused into a patient's peritoneal cavity and into contact with the patient's peritoneal membrane. Waste, toxins and excess water pass from the patient's bloodstream through the peritoneal membrane and into the dialysate. The transfer of waste, toxins, and excess water from the bloodstream into the dialysate occurs due to diffusion and osmosis during a dwell period as an osmotic agent in the dialysate creates an osmotic gradient across the membrane. The spent dialysate is later drained from the patient's peritoneal cavity to remove the waste, toxins and excess water from the patient.
Hemodialysis treatment removes waste, toxins and excess water directly from the patient's blood. The patient is connected to a hemodialysis machine and the patient's blood is pumped through the machine. Needles or catheters are inserted into the patient's veins and arteries to create a blood flow path to and from the hemodialysis machine. As blood passes through a dialyzer in the hemodialysis machine, the dialyzer removes the waste, toxins and excess water from the patient's blood and returns the cleansed blood back to the patient. A large amount of dialysate, for example about ninety to one hundred twenty liters, is used by most hemodialysis machines to dialyze the blood during a single hemodialysis therapy. Spent dialysate is discarded. Hemodialysis treatment lasts several hours and is generally performed in a treatment center about three times per week.
Another type of renal failure therapy is referred to generally as continuous renal replacement therapy (“CRRT”). While HD primarily relies upon diffusion to remove unwanted solutes, CRRT is a collection of subtherapies that utilize diffusion and/or convection in order to generate solute clearance, balance pH and fluid removal. During one type of CRRT, blood flows through a filter, such that a transmembrane pressure gradient between the blood compartment and the ultrafiltrate compartment causes plasma water to be filtered across the highly permeable membrane. As the water crosses the membrane, it can convect small and large molecules across the membrane and thus cleanse the blood.
CRRT has certain advantages relative to traditional dialysis therapies. A foremost advantage is the potential to effectively avoid, or at least minimize, cardiovascular instability. CRRT, in general, is a slow and continuous therapy that does not include rapid shifts in blood volume and electrolyte concentration due to the removal of metabolic products from blood as compared to intermittent forms of dialysis therapy, such as hemodialysis. Examples of continuous renal replacement therapies include continuous arteriovenous hemofiltration, continuous arteriovenous hemodialysis, continuous arteriovenous hemodiafiltration, continuous venovenous hemofiltration, continuous venovenous hemodiafiltration, continuous venovenous hemodialysis, slow continuous ultrafiltration, hemoperfusion and continuous ultrafiltration with periodic intermittent hemodialysis.
Hemofiltration, one type of CRRT, is an effective convection-based blood cleansing technique. Blood access can be venovenous or arteriovenous. As blood flows through the hemofilter, a transmembrane pressure gradient between the blood compartment and the ultrafiltrate compartment causes plasma water to be filtered across the highly permeable membrane. As the water crosses the membrane, it convects small and large molecules across the membrane and thus cleanses the blood. A large amount of plasma water is eliminated by filtration. Therefore, in order to keep the body water balanced, fluid must be substituted continuously by a balanced electrolyte solution (replacement or substitution fluid) infused intravenously. This substitution fluid can be infused either into the arterial blood line leading to the hemofilter (predilution), into the venous blood line leaving the hemofilter (postdilution) or both. Another type of therapy, hemodiafiltration, combines the diffusion and convective cleansing modes of hemodialysis and hemofiltration. The present invention expressly applies to each of the therapies mentioned herein including, additionally TPE, cytopheresis and hemoperfusion.
Each of the renal failure therapies involves the flow and control of multiple fluids. Some commercially available replacement or substitution fluids, for example, are lactate-based solutions. In certain instances, such as with patients with multiple organ failure, the use of the physiological buffer bicarbonate is preferred over lactate. It is common practice to manually prepare solutions buffered with bicarbonate extemporaneously. This is typically carried out by adding the prepared bicarbonate solution to an existing injectable quality solution to form the bicarbonate-based solution prior to administration to the patient. For example, it is known to add bicarbonate to an acidic electrolyte concentrate solution, which is in direct contact with administration tubing connected to the patient prior to administration thereof to the patient. It is also common practice to manually inject other electrolytes, such as potassium chloride, directly and separately into the bicarbonate-based solution prior to administration. The physical handling of the fluids can become tedious and time-consuming.
It should be appreciated that for each of the above-described types of renal failure therapies, transferring and monitoring the flowrate and the total volume of fluid delivered for multiple types of fluids as well as adhering to certain therapy restrictions (e.g., a first fluid must be flowing to or from the patient to enable a second fluid to flow) each create a control dilemma. Managing a patient's total fluid balance often involves obtaining the patient's prescribed net fluid loss or gain and manually summing various fluid inputs and fluid outputs to arrive at a necessary removal rate, which is then entered into a renal failure therapy machine, such as a dialysis machine or a CRRT machine. For example, if a patient is prescribed to have a net fluid loss (ultrafiltrate removal above and beyond patient fluid input but taking into account other sources of fluid output) of two hundred milliliters (“ml”) per hour (“hr”), is receiving one hundred ml/hr of fluid via an intravenous (“IV”) pump and has fifty ml/hr of urine output, the operator would have to calculate and instruct the renal failure therapy machine to remove two hundred fifty ml/hr of ultrafiltrate above and beyond replacement of substitution fluid that is being delivered by the CRRT or dialysis machine, so that the net total volume of fluid (removed) over the hour is two hundred ml.
The above example used only one IV fluid. It is possible however to have multiple IV or administration fluid inputs, making the above-described process even more involved and error prone. A need therefore exists to provide an improved system for calculating, balancing, synchronizing and controlling the delivery of multiple fluids in a renal failure therapy.